Zimbra's spamassassin does not recognize cyrillic letters

My system is: Ubuntu 7.10, Zimbra 5.0.1 Open Source.

Rules like:
body LOCAL_TEST /рассылки/i
score LOCAL_TEST 3.0
is working correctly if word between slashes typed by latin letters only, but if it typed cyrrilic - rules doesn't work
Please help me to fix that misunderstanding of different codings.